1. Field of the Invention
The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus including an image forming element, for example, an imaging apparatus such as an image projection apparatus which is provided with an image pickup apparatus including an image pickup device for obtaining an image signal corresponding to light irradiated on an photoelectric conversion surface of the image pickup device itself and a display element for displaying an image to be projected on a screen, and also relates to a structure for vibrating an optical element arranged in front of an image forming element in such an imaging apparatus.
2. Description of the Related Art
In recent years, image qualities have been greatly improved in imaging apparatuses using an image forming element, such as image projecting apparatuses which include an image pickup apparatus using an image pickup device and a display element such as a liquid crystal. Therefore, such a serious problem occurs that dust adheres to a surface of an image forming element such as image pickup device and a display element, or to a surface of a transparent member (optical element) located in front of the image forming element and the dust causes a shadow on an image to be generated.
For example, a digital single-lens reflex camera with an interchangeable lens has a photographing optical system which is attachable and detachable to and from a camera main body. A user can change the photographing optical systems by arbitrarily attaching and detaching a desired photographing optical system to and from the camera main body when the user desires, which enables selective use of various photographing optical systems in a single camera main body. In the single-lens reflex camera, when the photographing optical system is detached from the camera main body, dust suspended in an ambient environment where the camera is placed invades the camera main body. There is another possibility that dirt and the like are generated during operation of various mechanisms arranged in the camera main body, such as a shutter and diaphragm mechanism that mechanically operates, so that there is concern about an influence caused by the dirt.
As is known, in conventional digital single-lens reflex cameras, in order to restrain adherence of dust and the like to a photoelectric conversion surface of an image pickup device, a dust-proof member configured of an optical element is arranged in front of the photoelectric conversion surface of the image pickup device. In such cameras, the space between the photoelectric conversion surface of the image pickup device and the dust-proof member is sealed and a standing wave having a predetermined amplitude is applied to the dust-proof member using vibration-applying means, thereby removing dust and the like adhered on the outer surface side of the dust-proof member.
An image pickup apparatus disclosed in Japanese Patent Application Laid-Open Publication No. 2007-282101 includes on one end portion of a dust-proof member a first comb-shaped electrode, and on the other end of the dust-proof member a second comb-shaped electrode and a vibration-absorbing member. A surface acoustic wave is generated by applying alternate current to the first comb-shaped electrode and the generated surface acoustic wave is made to travel to the second comb-shaped electrode and the vibration-absorbing member. In the image pickup apparatus, the second comb-shaped electrode and the vibration-absorbing member are provided to absorb the surface acoustic wave and restrain the occurrence of a reflected wave of the surface acoustic wave, thereby preventing the surface acoustic wave traveled by the reflected wave from becoming a standing wave.
Furthermore, an optical filter, which is applied to an image forming apparatus disclosed in Japanese Patent Application Laid-Open Publication No. 2007-218957, is arranged on a surface of an optical member and includes a base substrate configured of a piezoelectric member, a comb-shaped electrode provided on an end portion of the base substrate, a power supply that applies voltage to the electrode, and a vibration-absorbing member. By applying voltage to the electrode, a surface acoustic wave is generated on a surface of the base substrate and reflected wave is absorbed by the vibration-absorbing member.